Because of good property of superimposing the received signals from adjacent channels, the synthetic aperture focusing technique (SAFT) can further improve the signal characteristic of defects, which has been widely used in ultrasonic nondestructive testing (NDT). For the concrete blocks embedded with defects in relatively deep position, it′s hard to obtain the high-resolution imaging results using the traditional B-Scan method and the traditional SAFT method because of the weak reflection information caused by heavy attenuation. In order to improve the ultrasonic imaging quality of concrete, the relative attenuation coefficient of ultrasonic propagating in concrete is measured, and the amplitude compensation technique is introduced to enhance the weal ultrasonic echo. Then the compensated signals are processed using the SAFT method, and the ultrasonic imaging quality can be further improved. Artificial concrete experiments show that the proposed method has higher imaging resolution than the traditional imaging methods, and the reflections of defects at the bottom area are clearer. The experimental results, including the embedded iron pipe and wooden block, verify the effectiveness of the proposed method.